<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style type="text/css">
	#btn{
		width: 100px;height: 100px;background: white;
	}
	#box{
		width: 100px;height: 100px;background-color: red;
	}

</style>	
<script type="text/javascript">
	window.onload = function(){
		document.getElementById('btn').onclick = function(){
			document.getElementById('box').style.width = '300px';
			document.getElementById('box').style.height = '300px';
		};
	};
</script>
</head>
<body>
	<input type="button" name="clicl" id="btn" value="click">
	<div id="box"></div>

</body>
</html>
